Interactions between dimers of {1,1′-[o-phenyl-enebis(nitrilo- methyli-dyne)]di-2-naphtholato-4 O,N,N′,O′}-nickel(II)

Article abstract of DOI:10.1107/S0108270109044503

In the title compound, [Ni(C₂₈H₁₈N₂O ₂)], the Ni^II centre has a square-planar coordination geometry in which the Schiff base ligand acts as a cis-O,N,N′,O′- tetra-dentate ligand. The crystal structure

Full text of DOI:10.1107/S0108270109044503

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
interactions and C—Hꢀ ꢀ ꢀO hydrogen bonding lead to a two-
dimensional supramolecular network. Upon coordination to
the metal centre, the ligand undergoes a substantial stereo-
chemical change from significantly nonplanar to an almost
planar configuration. It has been found that the free ligand in
the solid state exists in both enol–imine and keto–amine forms
ISSN 0108-2701
Interactions between dimers of
(
Popovi c´ et al., 2001; Blagus; 2005), while in complex (I), the
two chelating rings apparently contain delocalized electrons.
0
{
1,1 -[o-phenylenebis(nitrilomethyli-
4
0
0
dyne)]di-2-naphtholato-j O,N,N ,O }-
nickel(II)
a
b
Anita Blagus and Branko Kaitner *
a
Department of Chemistry, J. J. Strossmayer University, Osijek, Franje Kuha cˇ a 20,
b
HR-31000 Osijek, Croatia, and Department of Chemistry, Laboratory of General
and Inorganic Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a,
HR-10002 Zagreb, Croatia
Correspondence e-mail: kaitner@chem.pmf.hr
Comparison of the bond lengths observed in free (Popovic
´
et al., 2001) and Ni-coordinated ligands (Table 1) shows no
Received 25 September 2009
Accepted 26 October 2009
Online 7 November 2009
significant differences except in the case of the C —O and
ar
C
distances are slightly longer than the standard imine C
N imine bond distances. In complex (I), the Cn11—Nn1
N
double bond (1.28 A; Allen et al., 1987), and the Cn2—On1
bond lengths are shorter than the typical C—O single bond
II
In the title compound, [Ni(C H N O )], the Ni centre has a
square-planar coordination geometry in which the Schiff base
˚
28
18
2
2
0
0
˚
(1.34 A; n = 1 or 2). Both the C—N and C—O bond distances
ligand acts as a cis-O,N,N ,O -tetradentate ligand. The crystal
structure is built up of centrosymmetric dimer units stacked
into chains along the [010] direction. Adjacent chains
associate via C—Hꢀ ꢀ ꢀO hydrogen bonding only, leading to a
two-dimensional sheet-like structure consisting of layers
parallel to (101). The cofacial dimeric complex contains an
Niꢀ ꢀ ꢀNi contact of 3.291 (4) A˚ .
Comment
Polydentate Schiff base ligands and their metal complexes
have been extensively studied because of their preparative
availability and structural variability (Dodziuk, 2002).
Compounds of this type having a delocalized system of
conjugated ꢀ electrons play an important role as building
blocks in new materials for nonlinear optical applications
(Schalley, 2007). Schiff bases are electronically and sterically
tunable, which makes them versatile ligands for investigating
the effects of ligand flexibility on the reactivity of complexes
containing these ligands (Szłyk et al., 1999). Tetradentate
Schiff base metal complexes may form trans- or cis-planar or
tetrahedral structures (Elmali et al., 2000). Nickel(II)
complexes of aromatic diamine Schiff bases generally display
either square-planar or slightly distorted square-planar coor-
dination (Fun et al., 2008). In comparison with salicylaldimine
metal complexes, structural data for naphthaldimines and
related complexes are quite rare. So far, the coordination
compounds of 2-hydroxy-1-naphthaldimine derivatives of tin
(
Teoh et al., 1997), iron (Elerman et al., 1997), chromium
Wang et al., 2006), ruthenium (Prabhakaran et al., 2006) and
Figure 1
(
a) The molecular structure of the dimeric nickel(II) complex, showing
the atom-numbering scheme. Displacement ellipsoids are drawn at the
0% probability level and H atoms are shown as small spheres of
(
copper (Xue et al., 2007) have been reported.
5
We report here the structure of a nickel(II) complex with a
naphthaldiminate-type ligand (Fig. 1) in which ꢀ–ꢀ stacking
arbitrary radius. (b) A perpendicular projection of the dimer complex
molecule, showing the offset arrangement of the monomeric units.
Acta Cryst. (2009). C65, m455–m458
doi:10.1107/S0108270109044503
# 2009 International Union of Crystallography m455

metal-organic compounds
in the coordinated ligand are intermediate between single-
and double-bond values. The remaining bond lengths and
angles are all typical of their types (Allen et al., 1987).
explain the seemingly anomalous insolubility of nickel(II)
bis(dimethylglyoxime) as compared with its copper analogue
(Godycki & Rundle, 1953). This interaction is not common,
occurring only rarely in the numerous Ni structures in the
Cambridge Structural Database (CSD; Allen, 2002). The
reported Ni—Ni distances in the CSD, based on a search for
bonded Ni atoms in tetracoordinated complexes with a set of
either N or N O nonbridging donor atoms, range from 2.808
II
The coordination of the Ni ion is square planar, with a cis-
0
0
O,N,N ,O donor set. The Ni—N and Ni—O bond lengths are
within the ranges expected for square-planar Schiff base Ni
complexes (Szłyk et al., 1999; de Castro et al., 2001). Similar
coordination geometry has been observed in analogous nickel
complexes with Schiff bases derived from o-phenylenediamine
and salicylaldehyde (Wang et al., 1994, 2003). The Ni—N
distances are longer than the Ni—O distances for complexes
with ligands in which the diimine bridge is aromatic, whereas
for those with two aliphatic C atoms the opposite is observed
4
2
2
˚
to 3.336 A. The shorter Ni—Ni distances are observed in
structures for which nonbonding repulsions of the ligands are
8
minimal (Berry et al., 2006). In the present case, the d –d
8
Niꢀ ꢀ ꢀNi interaction is weak, being a consequence of other
types of stronger intermolecular interactions. Such Niꢀ ꢀ ꢀNi
interactions are weaker than most covalent or ionic bonds, but
they are stronger than other van der Waals interactions, and
are roughly comparable in strength to typical hydrogen bonds
(Pyykk o¨ , 1997). Similar Niꢀ ꢀ ꢀNi distances [Niꢀ ꢀ ꢀNi =
(Azevedo et al., 1994). The Ni—N bond distances in Ni(salen)
complexes are slightly longer than those in Ni(naphthen)
complexes (Wojtczak et al., 1997).
In the title compound, the Ni atom is displaced from the
˚
least-squares plane through the N and O atoms by only
˚
3.3244 (4) A] are found in a naphthaldimine nickel(II)
0.0082 (3) A, and this planarity permits extensive ꢀ-electron
complex with an aliphatic bridging diamine unit (Akhtar,
1981) and in a range of analogous nickel Schiff base complexes
˚
[3.201 (1)–3.582 (1) A] with metal–metal interactions (Chak-
raborty et al., 2004).
delocalization. In spite of that, the terminal naphthalene
moieties retained the genuine quinoidal bond-length
˚
arrangement [Cn3—Cn4 = 1.352 (3) and 1.359 (3) A, respec-
tively, for n = 1 and 2; Allen et al., 1987]. The dihedral angle
ꢁ
The aromatic rings within the dimer complexes are
arranged face-to-face and there are indeed net repulsive
interactions between the ꢀ systems. If the adjacent dimer
molecules are laterally offset with regard to each other this
offset geometry increases the attractive forces between the ꢀ
systems to the extent that they can become more significant
than the repulsive forces (Hunter & Sanders, 1990).
In our case, the only attraction within the dimer is the
metal–metal interaction, whereas the peripheral atoms show
significantly larger separation than those more centrally
located, e.g. the four donor atoms. The interplanar distance
between the least-squares planes defined by the N and O
between the two six-membered chelate rings is 1.25 (8) .
The molecules of (I) form centrosymmetric dimers through
a weak metal–metal interaction with an Niꢀ ꢀ ꢀNi distance of
˚
.291 (4) A. This contact is out of the range for bond-length
3
values usually accepted for the Ni—Ni bond distance (2.38–
˚
.81 A; Peng & Goedken, 1976, and references therein). The
2
bond between two Ni atoms was first proposed in 1953 to
˚
atoms (3.163 A) is in the repulsive range for nonbonding
Figure 2
A projection of the crystal packing along the a axis, showing the
herringbone arrangement of the complex molecules. The dimers stack by
weak ꢀ–ꢀ interactions in columns spreading along the b axis. The shortest
dimer-to-dimer contacts are represented as dotted lines.
Figure 3
A view of the crystal packing, showing the interconnection of the parallel
3
(010) columns into (101) layers through the C24—H24ꢀ ꢀ ꢀO21(ꢃx + ,
2
1
2
3
2
y ꢃ , ꢃz + ) hydrogen bonds (shown as dotted lines).
ꢂ
m456 Blagus and Kaitner
18 2
[Ni(C28H N O
2
)]
Acta Cryst. (2009). C65, m455–m458

metal-organic compounds
interactions (Williams et al., 1968). The apparent nonbonding
repulsion of the peripheral naphthalene rings is observed, as
Table 2
Hydrogen-bond geometry (A, ).
˚
ꢁ
ii
indicated by the C17ꢀ ꢀ ꢀC28 [symmetry code: (ii) ꢃx, ꢃy,
D—Hꢀ ꢀ ꢀA
D—H
Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA
D—Hꢀ ꢀ ꢀA
ii
˚
ꢃz + 1] separation of ca 3.677 A and the C18ꢀ ꢀ ꢀC27
i
˚
separation of ca 3.582 A. The influence of the reciprocally
C24—H24ꢀ ꢀ ꢀO21
0.95
2.46
3.298 (3)
147
3
2
1
2
3
2
Symmetry code: (i) ꢃx þ ; y ꢃ ; ꢃz þ .
repulsive interactions of the peripheral naphthalene rings
leads to a slightly saddle-shaped conformation of particular
dimeric molecules. The adjacent dimers have a staggered
arrangement that minimizes repulsive interactions. The later is
shown by an interplanar separation shorter than that in
All H atoms were located in a difference map and then treated as
˚
riding in geometrically idealized positions, with C—H = 0.95 A and
˚
˚
U (H) = 1.2U (C).
iso eq
graphite (3.35 A), amounting to ca 3.251 A. These interactions
clearly visible in Fig. 2) could be recognized as offset ꢀ–ꢀ
Data collection: CrysAlis CCD (Oxford Diffraction, 2003); cell
refinement: CrysAlis RED (Oxford Diffraction, 2003); data reduc-
tion: CrysAlis RED; program(s) used to solve structure: SHELXS97
(
attractive forces existing between the dimer molecules exclu-
sively and linking the dimers into parallel columns spreading
along [010].
(
Sheldrick, 2008); program(s) used to refine structure: SHELXL97
Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997);
(
The crystals are built up of parallel (101) layers formed by
software used to prepare material for publication: WinGX (Farrugia,
999), PARST97 (Nardelli, 1996) and Mercury (Version 1.4; Macrae
et al., 2006).
[
010] columns linked by the C—Hꢀ ꢀ ꢀO hydrogen bond (Fig. 3
1
and Table 2). The apparent herringbone packing pattern
typical for arrays of fused aromatic rings (Desiraju &
Gavezzotti, 1989) is shown in Fig. 2.
Financial support by the Ministry of Science, Education and
Sport of the Republic of Croatia is gratefully acknowledged
(grant No. 119-1193079-3069).
Experimental
The title nickel complex was synthesized by template synthesis. A
solution of nickel(II) chloride hexahydrate (1 mmol) and 2-hydroxy-
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: GD3313). Services for accessing these data are
described at the back of the journal.
1-naphthaldehyde (2 mmol) in absolute ethanol and an ethanol
solution of o-phenylenediamine (1 mmol) were allowed to mix by
slow diffusion through chloroform. After one week, red crystals had
formed.
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˚
V = 1953.23 (5) A
3
[Ni(C28H
18
N
2
O
2
)]
M
r
= 473.15
Z = 4
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˚
a = 15.8669 (3) A
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2
˚
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Áꢅmax = 0.42 e A
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Table 1
Selected geometric parameters (A, ).
˚
ꢁ
Ni1—O11
Ni1—O21
Ni1—N11
Ni1—N21
1.8385 (17)
1.8266 (17)
1.846 (2)
O11—C12
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1.298 (3)
1.301 (3)
1.315 (3)
1.313 (3)
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ˇ
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O11—Ni1—O21
O11—Ni1—N11
O11—Ni1—N21
84.04 (7)
94.60 (8)
177.87 (8)
O21—Ni1—N11
O21—Ni1—N21
N11—Ni1—N21
178.60 (8)
94.32 (8)
87.05 (9)
(
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3
ꢂ
Acta Cryst. (2009). C65, m455–m458
Blagus and Kaitner
18 2
[Ni(C28H N O
2
)] m457

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ꢂ
m458 Blagus and Kaitner
18 2
[Ni(C28H N O
2
)]
Acta Cryst. (2009). C65, m455–m458